Germany appears to have drastically curtailed its open-door policy for migrants in 2016, turning away 13,000 people without valid documentation in the first six months, already 4,000 more than in the whole of 2015, official data showed on Tuesday.

Around 117,500 migrants were admitted in the same period, compared to a record of more than one million migrants entering the country last year, mainly across the border from Austria.

The bulk of the rejections happened at land entry points and Afghans, Syrians, and Iraqis made up the three largest groups of the total, the Interior Ministry data published at the request of the hard-left Die Linke party showed.

Chancellor Angela Merkel last month interrupted her summer break to defend her government's migration policy after two Islamist attacks by asylum seekers, saying that those fleeing conflicts and persecution have the right to asylum in Germany.

More than 2,500 Afghans, 1,300 Syrians, and 1,000 Iraqis were declined entry at border crossings in the January-June period, the ministry said. Iranians, Moroccans, Nigerians, Pakistanis, Gambians, Somalis and Algerians made up the rest of the top 10.

The number of people seeking asylum in Germany dropped drastically this year as a result of border closures in the Balkans, an EU-Turkey deal to stop sea arrivals in Greece and tougher asylum rules in Germany.

In July, 4,500 migrants arrived in Germany, less than half of the daily arrivals at the peak of the crisis in the fall of last year, German police said earlier this month, bringing the number of arrivals in the first seven months of the year to 122,000.

Migrants who arrive in Germany are first registered at reception centres where they have to wait for months before they can officially file an asylum application, creating a huge backlog and putting a strain on civil servants.

The influx has dented the popularity of Merkel's ruling conservatives and prompted the rise of an anti-immigration party.

Turkey has threatened to suspend its migrants' agreement with the European Union if there is no deal to grant visa-free travel to Turks. The number of migrants reaches Italy in boats from Libya has also been rising.